Breeding Owls Defecate Strategically

With a four-foot wingspan, the Eurasian eagle owl is a big bird with a big appetite — and a fecal output to match. Yet the owl's body waste does not always go to waste.

New research suggests that breeding eagle owls defecate strategically, using their excrement to erect "No Trespassing" signs within their territories.

Lees meer:

• LiveScience
• PLoS ONE
  

Say It In Song: Researcher Deciphers Meaning Within Bird Communication

To many people, bird song can herald the coming of spring, reveal what kind of bird is perched nearby or be merely an unwelcome early morning intrusion. But to Sandra Vehrencamp, Cornell professor of neurobiology and behavior, bird song is a code from which to glean insights into avian behavior.

Birds use song systems to communicate about mating and reproduction, territorial boundaries, age and even overall health. Vehrencamp studies them to decode which elements convey such essential information. With colleagues in the Bioacoustics Research Program at Cornell's Lab of Ornithology, she studies birds in such natural habitats as Costa Rica, Colombia and Bonaire.

Lees meer: Science Daily

Dialect use in large assemblies: a study in European starling Sturnus vulgaris roosts

Auteurs: Hausberger, Martine; Bigot, Emmanuel; Clergeau, Philippe
Bron: JOURNAL OF AVIAN BIOLOGY, Volume 39, Number 6, November 2008 , pp. 672-682(11)
Abstract: Dialects may signal social or population identity and increase tolerance within communities. We hypothesized that in European starling Sturnus vulgaris communal roosts, birds coming from the same breeding area, i.e. dialectal zone, might tend to stay together within the roost. Recordings were performed in the colonies, revealed in earlier studies, multiple dialects and small sectors where birds shared the same variants at the different levels.
We also performed recordings in different locations within night roosts. The dialects recorded in the roosts were the same as those recorded at nest sites during the day and they were not distributed randomly within roosts: birds from the same geographical diurnal origin would gather and stay together, either because they arrived together or were attracted to their dialect.
Although our results have to be confirmed by the study of identifiable individuals, we propose original lines of thought on roost structuring and on the role of song dialects.

Sib-sib communication and the risk of prey theft in the barn owl Tyto alba

Auteurs: Roulin, Alexandre; Colliard, Caroline; Russier, Flavien; Fleury, Matthieu; Grandjean, Valentin
Bron: JOURNAL OF AVIAN BIOLOGY, Volume 39, Number 6, November 2008 , pp. 593-598(6)
Abstract: Conflicts among siblings are widespread and their resolution involves complex physical and communication tools. Observations in the barn owl Tyto alba showed that siblings vocally communicate in the absence of parents to negotiate priority of access to the impending food resources that parents will bring. In the present paper, we hypothesize and provide correlative evidence that after a parent brought a food item to their progeny, sibling competition involves vocal sib-sib communication.
A food item takes a long time to be entirely consumed, and hence siblings continue to compete over prey monopolization even after parents gave a food item to a single offspring. When physical competition is pronounced and thereby the risk of prey theft is high, the individual that received a prey item consumes it in a concealed place. Concomitantly, nestlings vocalize intensely probably to indicate their motivation to siblings to not share their food item, since this vocal behaviour was particularly frequent in younger individuals for which the risk of being robbed is higher than in their older siblings.
Furthermore, nestlings consumed more rapidly a food item when their siblings vocalized intensely presumably because the intensity of siblings' vocalizations is associated with a risk of prey theft. Our correlative study suggests that sibling competition favoured the evolution of sib-sib communication under a wide range of situations.

Changing grass height alters foraging site selection by wintering farmland birds

Auteurs: Whittingham, MJ; Devereux, CL
Bron: BASIC AND APPLIED ECOLOGY 9 (6): 779-788 2008
Abstract:
Grassland is a valuable habitat for many farmland bird species, some of which have declined in Europe. Successful management of this habitat is important to benefit these species. Recent studies have suggested little correlation between food abundance and bird use in grasslands instead providing access to food may be crucial. We tested the importance of manipulating sward height (via mowing) on the distribution of wintering birds in agriculturally managed grass fields using two within-field experimental designs. In experiment 1, we investigated the effect of two treatments (mown once and control). In experiment 2. we investigated the effects of four treatments (mown once early. mown once late. mown early and late. and control).

Mown plots supported higher abundances of foraging kestrels, thrushes mid starlings. In contrast meadow pipits and grey herons preferred unmown plots with longer grass. These differences are probably explained by differing anti-predation strategies, increased food abundance for species that prefer above-ground invertebrates (e.g. more food for meadow pipits on longer swards) and increased food accessibility, on short grass swards (e.g. for starling, thrush spp.). There were limited effects of multiple mowing events on plot use suggesting one early winter mowing, treatment may suffice to create favourable conditions for species that prefer shorter swards.
Providing grassland heterogeneity should benefit a range of wintering farmland birds. Although we use mowing to change grass sward height, our findings may also apply at other times of year when livestock grazing may be a more practical solution.

(c) 2007 Published by Elsevier GmbH on behalf of Gesellschaft fur Okologie.

Why Some Bird Species Lay Only One Egg

Why do some species of birds lay only one egg in their nest, while others lay 10 or more?

A global study of the wide variation among birds in this trait, known as the "clutch size," now provides biologists with some answers. The study, published in the current issue of the journal PLoS Biology, combined data on the clutch sizes of 5,290 species of birds with information on the biology and environment of each of these species.

Lees meer:

• Science Daily
• PLoS Biology
  

Early bird gets the better song

Mothers transfer the gift of music to the first eggs of their brood.

Birds that come from the earlier eggs in a brood are more likely to be better singers, scientists have found.

In most bird species, song is used by males to demonstrate their fitness to potential mates, and many studies have shown that the healthiest males tend to sing the longest, loudest and most complex songs.

Masayo Soma — who researches biolinguistics at the Riken Brain Science Institute, in Wako, Japan — and her colleagues wanted to find out if the order in which birds hatch affects their song. "I expected to detect age hierarchy in song, because older siblings are stressed less and obtain more resources growing up," says Soma.

Lees meer: Nature News

Insect shortage leaves sparrows starving

One of Britain's best-known birds may be declining because its chicks have too little to eat.

Too few insects in summer means young house sparrows in towns and cities are starving in their nests especially when parent birds are trying to raise important second and third broods.

Increased development, the popularity of ornamental plants like Leylandii, the removal of trees and the conversion of front gardens for parking may explain the loss of insects in urban areas, new research suggests.

Lees meer: The RSPB

Spring migration dynamics and sex-specific patterns in stopover strategy in the Wood Sandpiper Tringa glareola

Auteurs: Yoko Muraoka, Christian H. Schulze, Mihaela Pavličev, Gábor Wichmann
Bron: JOURNAL OF ORNITHOLOGY, DOI 10.1007/s10336-008-0351-5
Abstract: Due to being a virtually monomorphic wader species, migration dynamics and sex-related migration patterns in the Wood Sandpiper (Tringa glareola) have rarely been investigated. We captured spring migrants at an important stopover site in northeastern Austria. Birds were individually color-marked, and sex was determined by an analysis of DNA from tail feather material.
 Among temporary residents (birds seen again after day of capture), males migrated on average 3 days earlier than females. However, since sexes did not differ in fat score, the length of stay and the proportion of transients (birds not seen again after day of capture) and temporary residents, we suggest that males and females adopt similar migration strategies in the spring.
The large number of transients captured as well as shorter stopover durations in later temporary residents indicate that Wood Sandpipers minimize time at this stage of their northbound migration. Temporary residents earlier in the season exhibited lower fat stores than later ones. Nevertheless, since the fat stores of transients and temporary residents were similar even after the progress of the season had been accounted for, we assume that Wood Sandpipers may afford to exhibit individual flexibility in migration strategy and the use of stopover sites, especially early in the season. This variability may be a necessary adaptation to cope with possible varying environmental conditions at dynamic and unpredictable inland stopover sites.
After having reached North Mediterranean regions, mean body mass of spring migrants gradually increases during successive stopovers, indicating that Wood Sandpipers follow a 'hopping' migration strategy. This emphasizes the high conservation value of even small artificial mudflat pools as important stepping stones in order to maintain a continuous network of wetland habitats for this continental migrant.

Social learning of hunting skills in juvenile marsh harriers Circus aeruginosus

Auteurs: Ignacy Kitowski, Maria Curie-Sklodowska
Bron: JOURNAL OF ETHOLOGY, DOI 10.1007/s10164-008-0123-y
Abstract: The impact of social factors on the improvement of hunting skills of juvenile marsh harriers during their first autumnal migration were studied in SE Poland. While foraging with adult birds, juveniles performed more dives on prey both in terms of number of trials and rates. Hunting sessions of juveniles were more efficient in the presence of adults than in the absence of adults.
Juveniles hunting with adults and other juveniles could select adequate habitat patches in which access to prey is easier.
The role of vertical and horizontal transmission of information in the development of hunting skills in juvenile marsh harrier were confirmed because faster development of hunting ability was achieved in the social hunting after the end of their postfledging dependency period.

Longer guts and higher food quality increase energy intake in migratory swans

Auteurs: van Gils, JA; Beekman, JH; Coehoorn, P; Corporaal, E; Dekkers, T; Klaassen, M; van Kraaij, R; de Leeuw, R; de Vries, PP
Bron: JOURNAL OF ANIMAL ECOLOGY 77 (6): 1234-1241 NOV 2008
Abstract:
1. Within the broad field of optimal foraging, it is increasingly acknowledged that animals often face digestive constraints rather than constraints on rates of food collection. This therefore calls for a formalization of how animals could optimize food absorption rates.

2. Here we generate predictions from a simple graphical optimal digestion model for foragers that aim to maximize their (true) metabolizable food intake over total time (i.e. including nonforaging bouts) under a digestive constraint.

3. The model predicts that such foragers should maintain a constant food retention time, even if gut length or food quality changes. For phenotypically flexible foragers, which are able to change the size of their digestive machinery, this means that an increase in gut length should go hand in hand with an increase in gross intake rate. It also means that better quality food should be digested more efficiently.

4. These latter two predictions are tested in a large avian long-distance migrant, the Bewick's swan (Cygnus columbianus bewickii), feeding on grasslands in its Dutch wintering quarters.

5. Throughout winter, free-ranging Bewick's swans, growing a longer gut and experiencing improved food quality, increased their gross intake rate (i.e. bite rate) and showed a higher digestive efficiency. These responses were in accordance with the model and suggest maintenance of a constant food retention time.

6. These changes doubled the birds' absorption rate. Had only food quality changed (and not gut length), then absorption rate would have increased by only 67%; absorption rate would have increased by only 17% had only gut length changed (and not food quality).

7. The prediction that gross intake rate should go up with gut length parallels the mechanism included in some proximate models of foraging that feeding motivation scales inversely to gut fullness. We plea for a tighter integration between ultimate and proximate foraging models.

Aerial flocking patterns of wintering starlings, Sturnus vulgaris, under different predation risk

Auteurs: Claudio Carerer, Simona Montanino, Flavia Moreschini, Francesca Zoratto, Flavia Chiarotti, Daniela Santucci, Enrico Alleva
Bron: ANIMAL BEHAVIOUR, doi:10.1016/j.anbehav.2008.08.034
Abstract: To test the hypothesis that variation in aerial flocking behaviour is adaptively related to predation risk, we described and quantified the flocking patterns of starlings, approaching two urban roosts, which differed in predation pressure (by peregrine falcons, Falco peregrinus).
We predicted that the higher predation pressure in one of the roosts would be reflected in larger and more compact flocks, thought to be less vulnerable to predation than small flocks. Incoming flocks, not under direct attack, were observed during winter for 53 days.
We identified 12 flocking shapes. Significantly higher frequencies of compact and large flocks were observed in the roost with high predation pressure, while small flocks and singletons were more frequent at the roost with low predation pressure. Similar patterns were observed in both roosts when other flocks displayed antipredator behaviour, even when far away and in the absence of the predator at the focal roost.
This may indicate that social information passed between flocks affects flocking decisions. Predation success was higher at the roost with low predation. These results suggest that aerial flocking patterns are affected by predation risk and possibly by the behaviour of other flocks in response to direct attacks.

Distribution pattern of an expanding Osprey ( Pandion haliaetus) population in a changing environment

Auteurs: Mei-Ling Bai, Daniel Schmidt, Eckhard Gottschalk, Michael Mühlenberg
Bron: JOURNAL OF ORNITHOLOGY, DOI 10.1007/s10336-008-0345-3
Abstract: We studied the nest site selection and distribution pattern at landscape level of the German Osprey population, and demonstrated how to test the predictions of the ideal free distribution theory and its derivatives on such an expanding population. Information about the location and breeding success of each Osprey nest site between 1995 and 2005 was collected through a long-term monitoring programme. Data of land cover types were acquired from the administrations of each federal state and the CORINE Land Cover database.
The results showed that Ospreys preferred landscapes with more water bodies and forests. Such sites were also occupied earlier and had higher local population density. However, in the study period of 11 years, there was a gradual shift from forest-dominated landscapes to agricultural land-dominated landscapes.
The breeding success increased over time, with no difference in the breeding success between pairs nesting on trees and poles, whereas there was higher breeding success at nest sites surrounded by more agricultural land and less forest. The more efficient foraging in eutrophic lakes in agricultural landscapes was the most likely cause for the higher breeding success.
The distribution pattern of the Ospreys did not match the resource allocation, which deviated from the models tested. We suggested that the proximate cues used for nest site selection mismatched site quality due to anthropogenic environmental changes.

An artificial nest experiment indicates equal nesting success of waders in coastal meadows and mires

Authors: Pehlak, H; Lohmus, A
Source: ORNIS FENNICA 85 (2): 66-71 2008
Abstract:
Degradation of the distinct, diverse and abundant wader communities in Estonian coastal meadows has been recorded along with the ceasing agricultural management there. At the same time, the same species have been occupying adjacent inland mires.
This study examined the possibility that waders are switching their habitat due to increased nest predation in coastal meadows. However, no differences in the average daily survival rates of artificial nests were found between meadows and mires.
Data on real wader nests indicated that artificial nests reflect the fate of real nests. We suggest that meadows may have lost a past safety advantage and now the breeders are re-settling according to the current habitat quality. However, given the general
decline of waders, the temporally increasing populations of mire breeders are hardly self-sustaining. Therefore, attempts to restore coastal meadows are crucial for the Baltic Populations of several wader species.

Can foraging birds assess predation risk by scent?

Auteur(s): Timothy C. Roth, Jonathan G. Cox, Steven L. Lima
Bron: Animal Behaviour, doi:10.1016/j.anbehav.2008.08.022
Abstract: Olfaction is commonly used by a variety of aquatic and terrestrial taxa to assess predation risk. However, with a few exceptions (e.g. procellariformes and New World vultures), the evidence for the ecological relevance of olfaction in birds is sparse and inconsistent. This is the case even though birds retain the proper anatomical and neurological structures needed to use olfaction.
Here, we examined whether a passerine bird responds to the chemical scent of predators in the laboratory. We exposed house finches, Carpodacus mexicanus, to the olfactory cues of predatory and nonpredatory mammalian faeces and observed their behavioural response while feeding. Finches responded to both predator and nonpredator faecal cues, but they responded to the predator cues more strongly in some analyses.
For example, in response to both faecal treatments, finches delayed their first feeding, spent less time on the feeder as a whole and reduced feeding bout length; the bout length effect was particularly pronounced in the predator treatment. Vigilance did not increase but instead decreased during the faecal treatments, which may have reflected a strategy of minimizing time on the feeder (where the cue was presented). The behavioural effects of faecal cues weakened quickly over time and were most evident during the first 5 min of an observational session.
Overall, our results show that finches can detect mammalian faecal cues and associate such cues with possible danger.

Within-season divorce in Common Terns Sterna hirundo in a year of heavy predation

Auteur(s): Sonja C. Ludwig, Peter H. Becker
Bron: JOURNAL OF ORNITHOLOGY,  Volume 149, Number 4 / October, 2008
Abstract: Divorce between seasons is a common phenomenon in seabirds, whereas within-season mate change is rarely observed. We report four cases of within-season mate change in renesting Common Terns Sterna hirundo during a year of heavy predation by a Long-eared Owl Asio otus, when we found more deserted clutches, lower hatching success as well as more disappeared chicks compared to other years. Within-season nest-site fidelity also decreased under predation pressure.

Birds in "Big Trouble" Due to Drugs, Fishing, More

Bird species are in "big trouble" worldwide, a sign that the planet's health is also faltering, according to a new report released today at the International Union for Conservation of Nature (IUCN) meeting in Barcelona, Spain.

Not only are rare birds getting rarer, but migratory songbirds, seabirds, and even common backyard birds are also plummeting, according to the State of the World's Birds, a report by the U.K. nonprofit BirdLife International.

Lees meer: National Geographic News

Singing To Females Makes Male Birds' Brains Happy

The melodious singing of birds has been long appreciated by humans, and has often been thought to reflect a particularly positive emotional state of the singer. Researchers at the RIKEN Brain Science Institute in Japan have now demonstrated that this can be true. When male birds sang to attract females, specific "reward" areas of their brain were strongly activated. Such strong brain activation resulted in a similar change in brain reward function to that which is caused by addictive drugs.

Lees meer: Science Daily

Wing-spreading, wing-drying and food-warming in great cormorants Phalacrocorax carbo

Auteur(s): Craig R. White, Graham R. Martin and Patrick J. Butler
Bron: JOURNAL OF AVIAN BIOLOGY 39 (5): 576-578 SEP 2008
Abstract: Wing-spreading of cormorants (Phalacrocoracidae) is a characteristic and enigmatic aspect of their behavioural repertoire. It has been suggested to have a range of functions including wing-drying, food-warming, and social signalling of foraging success. We investigated two of these putative roles by comparing the wing-spreading behaviour of fed and unfed animals after they had been swimming and diving. The duration of wing-spreading was correlated only with time spent on the water. The ingestion of food did not influence the duration of wing-spreading, a finding that supports a wing-drying, rather than a food-warming, function.

Identifying predators of eggs and chicks of Lapwing Vanellus vanellus and Black-tailed Godwit Limosa limosa in the Netherlands and the importance of predation on wader reproductive output

Auteur(s): Wolf Teunissen, Hans Schekkerman, Frank Willems, Frank Majoor
Bron: IBIS 150: 74-85 Suppl. 1 AUG 2008
Abstract: Farmland bird populations in the Netherlands have shown an accelerating decline in recent years, despite extensive conservation efforts including reserves, agri-environment schemes and protection of nests by volunteers. Although agricultural intensification is the main cause underlying these declines, there is a growing concern that the ongoing decline of grassland-breeding shorebirds in recent years is caused or aggravated by increasing predation. Although Red Fox Vulpes vulpes and Carrion Crow Corvus corone are often accused of causing widespread breeding losses, and calls for management of these species are made, very few field data are available on the incidence of predation on grassland shorebirds and the relative importance of different predators.
To obtain such data, we identified egg predators using temperature loggers and continuous video recordings of 792 clutches, and chick predators by radiotagging 662 chicks of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus. In total, 22 species were identified as predators of eggs or chicks, of which Red Fox, Common Buzzard Buteo buteo, Grey Heron Ardea cinerea and Stoat Mustela erminea were the most frequent. Eggs were taken primarily by mammals and chicks more often by birds.
There was great variation in predation levels and species involved in predation of clutches between sites and years, but less in chick predation. Hence, there was no correlation between predation levels on clutches and those on chicks within the same sites. In sites where more then 50% of clutches were lost to predation, however, nocturnal predators took the larger share.
As temporal and spatial variation on a small scale significantly influences predation levels, a site-specific approach based on sound knowledge of the local situation will be more effective in reducing predation on farmland birds than general, country-wide measures. Calculations based on our data indicate that eliminating only one loss factor at a time will often not reverse a local population decline, and provide a strong argument for targeting several locally limiting factors simultaneously instead of focusing on mitigation of predation alone.

Ecologists Allay Fears For Farmland Birds From Wind Turbines

Wind farms pose less of a threat to farmland birds than previously
feared, new research has found. The study, published this week in the
British Ecological Society's Journal of Applied Ecology, helps resolve
a potentially major environmental conflict: how to meet renewable
energy targets at the same time as reversing dramatic declines in
biodiversity on European farmland.

Lees meer: Science Daily

Scavenger Birds Chew The Fat

Humans aren’t the only ones who like fatty foods - bearded vultures do, too. A study by Antoni Margalida from the Bearded Vulture Study and Protection Group in El Pont de Suert, Spain, has found that the bearded vulture will discard less energy-dense bones and choose only the bones containing the highest fat content both for its consumption and delivery to its young.

Lees meer: Science Daily

Food shortages produce chick-killing auks

One of Britain's commonest auks is increasingly attacking and killing neighbouring chicks in response to food shortages at seabird colonies on a Firth of Forth island.

Researchers at the University of Leeds and the Centre for Ecology & Hydrology, who have been studying Common Guillemots on the Isle of May in Scotland, have observed a dramatic increase in the number of adults deliberately attacking chicks in neighbouring nests.


Lees meer: Birdwatch

Do small hole nesting passerines detect cues left by a predator? A test on winter roosting sites

Auteur(s): Ekner, A; Tryjanowski, P
Bron: ACTA ORNITHOLOGICA, 43 (1): 107-111; SUM 2008
Abstract: There are a lot of studies about relationships between prey and predators. However most have focused on the influence of lethal predators on their prey. We suggested that non-lethal effects may also be very important for a complete understanding of prey-predator interactions.
Among many influencing factors predation is important because it affects survival probability, especially in winter, which is a critical period for many passerines living in temperate zones. Apart from killing prey, predators may also have an indirect influence on the choice of nocturnal resting sites. Therefore, small passerines should detect and avoid places where a predator has operated previously. We tested this prediction using data on wintering small passerines, mainly on Great Tits.
The study was performed during the winter season of 2005/2006 in western Poland. In the experiment, we put fur and mangled feathers in half of 100 randomly selected nest boxes. Boxes were checked every ten days, from January-March. The birds showed a significantly stronger preference towards "clean" nest boxes (without predator traces). It seems that non-lethal predator influence modifies winter dispersion of birds and wintering passerines may detect, by Visual signals left behind, nest boxes where predation has previously occurred.

The establishment of an urban bird population

Auteur(s): Rutz, C
Bron: JOURNAL OF ANIMAL ECOLOGY, 77 (5): 1008-1019; SEP 2008
Abstract:
1. Despite the accelerating global spread of urbanized habitats and its associated implications for wildlife and humans, surprisingly little is known about the biology of urban ecosystems.

2. Using data from a 60-year study period, this paper provides a detailed description of how the northern goshawk Accipiter gentilis L. - generally considered a shy forest species - colonized the city of Hamburg, Germany. Six non-mutually exclusive hypotheses are investigated regarding the environmental factors that may have triggered this invasion.

3. The spatio-temporal analysis of 2556 goshawk chance observations (extracted from a total data set of 1 174 493 bird observations; 1946-2003) showed that hawks regularly visited the city centre decades before the first successful breeding attempts were recorded. Many observations were made in parts of the city where territories were established in later years, demonstrating that these early visitors had encountered, but not used, potential nest sites.

4. Pioneer settlement coincided with: (i) an increase in (legal) hunting pressure on goshawks in nearby rural areas; (ii) an increase in avian prey abundance in the city; and (iii) a succession of severe winters in the Greater Hamburg area. On the other hand, there was no evidence to suggest that the early stages of the invasion were due to: (i) decreasing food availability in rural areas; (ii) major habitat changes in the city; or (iii) rural intraguild dynamics forcing hawks into urban refugia. While breeding numbers of a potential rural source population were at a long-term low when the city was colonized, prior to first settlement there was a sharp increase of goshawk chance observations in the city and its rural periphery.

5. The urban population expanded rapidly, and pair numbers began to stabilize after about 10 years. Ringing data (219 ringed nestlings from 70 urban broods; 1996-2000) demonstrated that most urban recruits had fledged in the city, but also confirmed considerable gene flow between urban and rural habitats. Analysis of chance observations (as raw data or as detrended time series) suggested a tight coupling of population dynamics inside and outside the city.

6. City-colonizations such as the one described here provide a valuable opportunity to study some fundamental aspects of population ecology on a scale at which detailed monitoring is logistically feasible. Furthermore, a good understanding of urban ecology has become essential for efficient wildlife conservation in modern, human-altered environments.

French birds moving north too slowly

A new study of breeding birds in France has concluded that they are moving their range north more slowly than other effects of climate change that are influencing them.

Lees meer: Birdwatch / BBC News

Verdwijnen lemmingen ramp voor broedende ganzen

De Taimyr expeditie is weer terug uit Siberië. Van begin juni tot midden augustus onderzocht dit internationale onderzoeksteam van Alterra en het NIOO de relaties tussen pooldieren en de rol van het klimaat hierin.
Afgelopen zomer bleek rampzalig voor broedende ganzen. Een vroeg instortende lemmingenpopulatie veroorzaakte honger bij middelste jagers en sneeuwuilen, die hierdoor geen eieren legden en hun territoria niet verdedigden. Hierdoor gaven ze poolvossen vrije toegang tot het anders zo veilige broedgebied van de ganzen.
Ook Taimyrmeeuwen leden honger door het gebrek aan lemmingen en roofden ganzeneieren en –pullen. Tenslotte werden er veel rotgansnesten weggespoeld door grote hoeveelheden smeltwater.


Lees meer: Natuurbericht.nl

Nethy & Deshar

We're tracking two osprey chicks, Nethy and Deshar, from their nest at Loch Garten, Scotland as they migrate for the first time.

Follow the highs and lows of their journey with us right here.


The RSPB: Loch Garten Ospreys

Mirror Self-recognition In Magpie Birds

Self-recognition, it has been argued, is a hallmark of advanced cognitive abilities in animals. It was previously thought that only the usual suspects of higher cognition—some great apes, dolphins, and elephants—were able to recognize their own bodies in a mirror.

Psychologist Helmut Prior and colleagues have shown evidence of self-recognition in magpies—a species with a brain structure very different from mammals.

Lees meer: Science Daily

Owls May Use Faeces and Prey Feathers to Signal Current Reproduction

by Vincenzo Penteriani, Maria del Mar Delgado

Background

Many animals communicate by marking focal elements of their home range with different kinds of materials. Visual signaling has been demonstrated to play a previously unrecognized role in the intraspecific communication of eagle owls (Bubo bubo), in both territorial and parent-offspring contexts. Visual signals may play a role in a variety of circumstances in this crepuscular and nocturnal species.

Methodology/Principal Findings

Here, we report that a large amount of extremely visible white faeces and prey feathers appear during the breeding season on posts and plucking sites in proximity to the nest, potentially representing a way for eagle owls to mark their territory. We present descriptive and experimental evidence showing that faeces and prey remains could act as previously unrecognized visual signals in a nocturnal avian predator. This novel signaling behavior could indicate the owls' current reproductive status to potential intruders, such as other territorial owls or non-breeding floaters. Faeces and prey feather markings may also advertise an owl's reproductive status or function in mate-mate communication.

Conclusions/Significance

We speculate that faeces marks and plucking may represent an overlooked but widespread method for communicating current reproduction to conspecifics. Such marking behavior may be common in birds, and we may now be exploring other questions and mechanisms in territoriality.

Lees meer: PLoS One

Raptors Survival Can Be Threatened By Ingesting Lead And Cadmium

Birds of prey accumulate environmental pollutants distributed in the surroundings and, in some cases, these can cause death. A comparative study of raptors in Galicia and Extremadura undertaken by Spanish researchers has confirmed their exposure to two potentially toxic agents, lead (Pb) and cadmium (Cd). The data obtained can be used to detect the toxicological effects in terrestrial ecosystems.

Birds of prey that live in extensive geographical areas can accumulate high levels of heavy metals and metalloids in their bodies, as they are top of their food chain. Now researchers from the Universidad de Extremadura and from the Universidad de Santiago de Compostela can reveal that these wild animals can provide extremely useful data to detect and evaluate the toxicological effects of different inorganic elements in terrestrial ecosystems. This information could also be extrapolated to human beings.

Lees meer: Science Daily

Sustained bird flights occur at temperatures far beyond expected limits

Auteur(s): Heiko Schmaljohann, Bruno Bruderer, Felix Liechti
Bron: ANIMAL BEHAVIOUR, doi:10.1016/j.anbehav.2008.05.024
Abstract: Migratory birds deposit fat and protein before passing ecological barriers and must economize these during such crossings. Birds crossing the western Sahara during autumn face a trade-off between cold and humid air along with head winds at high altitudes versus warm and dry air along with tail winds at low altitudes. Since water loss rate increases with temperature, migrants should avoid warm and dry air to save water and hence fly at high altitudes.
By quantifying nocturnal songbird migration across the western Sahara with radar, we found that more than 60% of the songbirds migrated below 1000 m above ground level. Thus, the majority of songbirds performed sustained migratory flights in much warmer and drier conditions than predicted (weighted means: 30 °C; relative humidity: 27%; water vapour density: 7.8 g/m3). Based on the metabolically available water from fat and protein catabolism, we estimated the maximum possible overall water loss rate of a flying model bird, the garden warbler, Sylvia borin, for the entire Sahara crossing at 0.29 g/h. This is considerably lower than water loss rates for the same model bird passing our study site, 0.62 g/h at 30 °C, based on applied calculations of physiological studies.
Our results clearly show that migrating songbirds can fly at much higher temperatures, and have considerably lower water loss rates, than predicted. This new insight based on observations under natural conditions will have substantial impact on the development of new physiological models for birds and other animals with restricted access to water.

The impact of raptors on the abundance of upland passerines and waders

Auteur(s): Arjun Amar, Simon Thirgood, James Pearce-Higgins, Steve Redpath
Bron: OIKOS Volume 17 Issue 8, Pages 1143-1152
Abstract: The issue of predator limitation of vertebrate prey populations is contentious, particularly when it involves species of economic or conservation value. In this paper, we examine the case of raptor predation on upland passerines and waders in Scotland. We analysed the abundance of five wader and passerine species on an upland sporting estate in southern Scotland during an eight-year period when hen harrier, peregrine and merlin numbers increased due to strict law
enforcement.
The abundance of meadow pipit and skylark declined significantly during this time. Golden plover also showed a declining trend, whereas curlew increased significantly and there was a near significant increase in lapwings. Contrasting the local population
trends of these species with trends on nearby areas revealed higher rates of decline for meadow pipit and skylark at the site where raptors increased, but no differences in trends for any of the three wader species.
There was a negative relationship between the number of breeding harriers and meadow pipit abundance the same year and between total annual raptor numbers and meadow pipit abundance. Predation rates of meadow pipit and skylark determined from observations at harrier nests suggested that predation in June was sufficient to remove up to
40% of the June meadow pipit population and up to 34% of the June skylark population.
This 'quasi-natural' experiment suggests that harrier predation limited the abundance of their main prey, meadow pipit, and possibly the abundance of skylark. Thus, high densities of harriers may in theory reduce the abundance of the prey species which
determine their breeding densities, potentially leading to lower harrier breeding densities in subsequent years. We found no evidence to suggest that raptor predation limited the populations of any of the three wader species. We infer that concerns over the impact of natural densities of hen harriers on vulnerable upland waders are unjustified.

Trawling: a major threat to albatrosses

A study of trawl fishing in South Africa suggests that around 18,000 seabirds may be killed annually in this fishery, highlighting trawl fisheries as a major threat to seabirds, especially several species of albatross already facing a risk of extinction.

Lees meer: The RSPB

Going, Going, Gone: Is Animal Migration Disappearing

Animal migration surely ranks as one of nature's most visible and widespread phenomena. Every minute of every day, somewhere, some place, animals are on the move. The migrants span the animal kingdom, from whales and warblers to dragonflies and salamanders. But is migration an endangered phenomenon? Around the world, many of the most spectacular migrations have either disappeared due to human activities or are in steep decline. Those of us living in eastern North America can no longer experience the flocks of millions of passenger pigeons that temporarily obscured the sun as they migrated to and from their breeding grounds. Nor can residents of the Great Plains climb to the top of a hill and gaze down up hundreds of thousands of bison trekking across the prairies, as was possible less than two centuries ago.

Lees meer: PLoS Biology

When to be a dear enemy: flexible acoustic relationships of neighbouring skylarks, Alauda arvensis

Auteur(s): Elodie Briefer, Fanny Rybak, Thierry Aubin
Bron: ANIMAL BEHAVIOUR doi:10.1016/j.anbehav.2008.06.01
Abstract: Numerous territorial species are less aggressive towards neighbours than strangers. This tolerance towards neighbouring conspecifics, termed the ‘dear enemy’ effect, seems to be a flexible feature of the relationship between neighbours, and has been shown to disappear in some species after experimental or natural modifications of the context. However, the maintenance over time of this singular relationship has been poorly studied.
In this study, we followed the change of dear enemy relationships during the breeding season in a territorial songbird with a complex song, the skylark. We examined in the field the response of territory owners to playbacks of neighbour and stranger songs at three periods of the breeding season, corresponding to three ecological and social situations.
Results showed that neighbours were dear enemies in the middle of the season, when territories were stable, but not at the beginning of the breeding season, during settlement and pair formation, nor at the end, when bird density increased owing to the presence of young birds becoming independent. Thus, the dear enemy relationship is not a fixed pattern but a flexible one likely to evolve with social and ecological circumstances.

Within-brood social status and consequences for winter hierarchies amongst Mallard Anas platyrhynchos ducklings

Auteur(s): Maud Poisbleau, Matthieu Guillemain, Laurent Demongin, David Carslake, Joan David
Bron: JOURNAL OF ORNITHOLOGY DOI 10.1007/s10336-008-0334-6
Abstract: Juveniles of many birds establish dominance hierarchies within family social units, only to leave and compete to acquire dominance status in new social groups. Little is known about the role of sex, body mass, size or experience during the duckling period on subsequent dominance rank and adult social relationships.
We used captive Mallard Anas platyrhynchos ducklings to test for the role of individual characteristics and growth parameters in establishing within-brood hierarchies, the maintenance of within-brood hierarchies in the subsequent wintering group and differences in social ranks between broods. Strong stable linear hierarchies were present within each brood and, later, within each phase of the winter. There was a reorganisation of the hierarchical order between the duckling period and early winter, but only few modifications afterwards during the winter.
None of the tested "hatching", "duckling" and "adult" traits explained either the within-brood or the winter hierarchies, but winter rank was related to brood of origin with ducklings from the same brood having similar social ranks. These differences between broods were maintained through the whole winter in most cases, though one brood drastically progressed in the hierarchy during late-winter.
These results suggest that the factors affecting the establishment of social relationships within broods differ from those in winter groups, and that brood-related mechanisms influence social relationships during winter. We discuss our results in the light of direct and indirect maternal influence.

Avian Cooperation: Rooks Work Together to Solve Puzzle for Food

Birds of a feather don’t just flock together—they also work together to obtain food. Recent research makes rooks the first nonprimates observed to successfully cooperate to retrieve a food-laden platform, according to a June 22 study in the journal Proceedings of the Royal Society B: Biological Sciences.

Lees meer: Scientific American

Birdsong Not Just For The Birds: Bio-acoustic Method Also Hears Nature’s Cry For Help

Switch on the mike, start the recording, the stage is set for the local fauna!

Computer scientists from the University of Bonn, in conjunction with the birdsong archives of Berlin’s Humboldt University, have developed a kind of ‘Big Brother’ for birds. This has nothing to do with entertainment, but a lot to do with the protection of nature. The new type of voice detector involved can reliably recognise the characteristic birdsong of different species of birds, thereby facilitating surveys of the bird population.

Europe’s forests are falling silent as countless species of birds go on the red list of endangered species. Yet in fact no-one can say what the exact position is with some species. So as to have a reliable count of the territories of indigenous birds it would practically be necessary to send out a whole horde of spare-time ornithologists to count the birds. What is more, since the birds are often hidden in the undergrowth or the tree tops, ornithologists need to rely on their ears and their specialist knowledge. This means that in many areas it is wellnigh impossible to map the bird population comprehensively and continuously.

Lees meer: Science Daily

Space use by Black-tailed Godwits Limosa limosa limosa during settlement at a previous or a new nest location

Auteur(s): Van Den Brink, V; Schroeder, J; Both, C; Lourenco, PM; Hooijmeijer, JCEW; Piersma, T
Bron: BIRD STUDY, 55: 188-193, Part 2; JUL 2008
Abstract: Black-tailed Godwits first return to the nest location of the previous year, even when moving to a different nest location later that season.

Aims: To examine the use of space by Black-tailed Godwits during the two months before egg-laying to two weeks afterwards.

Methods: We compare the spatial distribution of sightings of eventually site-faithful birds with birds that changed nest location, and relate this to the change of the distance to their previous year's and current nest-site in the period until egg-laying. Using a log-likelihood model we establish how the differences in distance to the respective nests change over the course of the season.

Results: All birds were observed first near their previous year's nest-site, and remained there for most of the pre-laying period. Birds that subsequently changed nest location made the move only about five days before egg-laying and were more wide-ranging earlier on.

Conclusion: The return to the previous nest-site suggests that a decision to move is made only after considerable time investment near the previous nest-site. This indicates that site-faithfulness in Black-tailed Godwits is conditional on experiences after return to the nesting area.

Bird evolutionary tree given a shake by DNA study

A new study – the largest analysis of birds to date using modern genetic methods – has turned up numerous surprising relationships that will force biologists to reevaluate much of what they thought they knew about avian evolution.

Until now, this evolutionary history has been something of a mystery, because most modern orders of birds arose in a sudden burst of innovation sometime between 65 and 100 million years ago. This left few intermediate forms to help biologists discern the evolutionary relationships among orders.

Lees meer: New Scientist

Acoustic information as a distant cue for habitat recognition by nocturnally migrating passerines during landfall

Auteur(s): Andrey Mukhin, Nikita Chernetsov, Dmitry Kishkinev
Bron: Behavioral Ecology 2008 19(4):716-723; doi:10.1093/beheco/arn025
Abstract: During migration, birds must fly over suboptimal habitats differing from those selected during breeding and wintering. Nocturnally migrating passerines need to assess the suitability of potential stopover habitats during landfall. Before actual landfall, distant cues may play a significant role in habitat selection.
In this paper, we studied the possibility that migrant songbirds use acoustic information as distant cues for habitat selection when ceasing flight. We also investigated differences between habitat generalists and specialists in their use of acoustic cues by comparing the proportion of species killed at lighthouses with those captured in mist nets using song playback in both suitable habitats and suboptimal stopover habitats during spring and fall migratory seasons.
Our observations showed that during twilight landfall, birds may respond to acoustic cues, especially when visual cues are reduced or absent. This was true for habitat specialists (Eurasian reed warblers and sedge warblers) whose songs are also more attractive to conspecifics and other birds of wetland habitats than to habitat generalists (pied flycatchers and redwings). Adult Eurasian reed warblers had a tendency to be more attracted by acoustic cues than juveniles. This finding suggests that previous experience may play a role in habitat recognition using acoustic stimuli.

Do birds have a good sense of smell?

Birds don't just see and hear well, their sense of smell is also highly developed.
The sense of smell might indeed be as important to birds as it is to fish or even mammals. This is the main conclusion of a study by Silke Steiger (Max Planck Institute for Ornithology) and her colleagues.

The sense of smell in birds was, until quite recently, thought to be poorly developed. Recent behavioural studies have shown that some bird species use their sense of smell to navigate, forage or even to distinguish individuals. Silke Steiger and her colleagues chose a genetic approach for their study. Their research focused on the olfactory receptor (OR) genes, which are expressed in sensory neurons within the olfactory epithelium, and constitute the molecular basis of the sense of smell. The total number of OR genes in a genome may reflect how many different scents an animal can detect or distinguish. In birds such genetic studies were previously restricted to the chicken, hitherto the only bird for which the full genomic sequence is known.

Lees meer: Eurekalert

Mortality of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus chicks in wet grasslands: influence of predation and agriculture

Auteur(s): Hans Schekkerman, Wolf Teunissen, Ernst Oosterveld
Bron: JOURNAL OF ORNITHOLOGY DOI10.1007/s10336-008-0328-4
Abstract: Grassland-breeding shorebirds show widespread declines due to a reduction in breeding productivity following agricultural intensification. However, there is also concern that increasing predation causes further declines or precludes population recovery. Predation may itself be enhanced by agriculture through changes in habitat or food availability, but little is known about the mortality of nidifugous shorebird chicks. We studied mortality by radio-tagging 662 chicks of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus in 15 farmland sites in the Netherlands. Tagging and handling had no effect on the condition and survival of godwit chicks, but body condition was reduced by 6–11% in lapwing chicks wearing a tag for longer than 3 days. Fledging success was 0–24% in both species.
Mortality was highest in young chicks but remained considerable until after fledging. Losses were traced mostly to predators (70–85%; 15 species, predominantly birds), but at least 5–10% were due to mowing, and 10–20% were due to other causes, including entrapment in ditches and starvation. Chicks staying in fields that were cut before the next radio check were found much more often as mowing victims and somewhat more often as prey remains than chicks in fields not cut, indicating that predation includes a limited amount of scavenging. The predation hazard for godwit chicks was higher in recently cut or grazed fields than in the tall, uncut grasslands they preferred, while that for lapwing chicks was lowest in grazed fields. In godwit chicks, poor body condition increased mortality risk, not only from starvation but also from other causes. Predation on godwit chicks was thus enhanced by intensive farming through a decline in the availability of cover, augmented by a reduced body condition, possibly due to food availability problems.
Changes in farming practice may therefore help reduce predation pressure, though the observed interactions explained only part of the high predation rate in godwits and none in lapwings. Predator abundance has increased in Dutch wet grassland regions, and chick predation has become a factor that should be considered in planning the type and location of conservation measures.

Reed warblers discriminate cuckoos from sparrowhawks with graded alarm signals that attract mates and neighbours

Auteur(s): J.A. Welbergen, N.B. Davies
Bron: ANIMAL BEHAVIOUR, doi:10.1016/j.anbehav.2008.03.020
Abstract: Brood parasites and predators pose unique threats that may favour the evolution of enemy-specific defence strategies. We considered whether reed warblers, Acrocephalus scirpaceus, have a specific alarm call for common cuckoos, Cuculus canorus, and whether their alarms attract mates and neighbours. Mounts of cuckoos (threat to nest but harmless to adults) were significantly more likely to be mobbed and were mobbed more strongly, with rasp calls and mandible snaps, than mounts of sparrowhawks, Accipiter nisus (threat to adults only), or teal, Anas crecca (a harmless control). However, calls were not acoustically specific to the kind of enemy presented, but rather varied in usage with mount distance from the nest and mount species.
This suggests that reed warbler alarm signals are not functionally referential, but rather convey immediacy of threat to the nest. Mates and neighbours often approached during calling, and playback experiments confirmed they were more likely to be attracted by mobbing calls than by control calls. The response was graded, with higher repetition rates of mobbing calls attracting more individuals. Nevertheless, it is unlikely that mobbing calls functioned solely to attract mates and neighbours because calling continued even after these were attracted and was not more likely when there were close neighbouring nests, and attracted neighbours were sometimes chased away by residents.
Our results show that reed warblers discriminate a brood parasite from both a dangerous species and an innocuous species by using graded alarm signals that attract conspecifics. This is compatible with the idea that nest defence by reed warblers includes a specific evolved response to brood parasitism.

Faux Hawk: Why Do Cuckoos Mimic Raptors?

Cuckoos are notorious freeloaders, conning other species into rearing their young, often at the expense of the hosts' chicks. But a new study suggests that the parasitic birds are not mere opportunists.

Like thieves who yell "fire" to clear a store before robbing it, cuckoos appear to have evolved hawklike plumage patterns and physical traits that temporarily scare potential hosts from their nests so they can lay eggs in them and get other birds to rear them.

Lees meer: Scientific American

Does ambient noise affect growth and begging call structure in nestling birds?

Auteur(s): Marty L. Leonard and Andrew G. Horn
Bron: Behavioral Ecology 2008 19(3):502-507; doi:10.1093/beheco/arm161
Abstract: Much of the research examining the effects of ambient noise on communication has focused on adult birds using acoustic signals in mate attraction and territory defense. Here, we examine the effects of noise exposure on young birds, which use acoustic signals to solicit food from parents.
We found that nestling tree swallows (Tachycineta bicolor) exposed to playbacks of white noise, within natural amplitude levels, from days 3 to 15 posthatch had begging calls with higher minimum frequencies and narrower frequency ranges than control nestlings raised in nests without added noise. Differences in begging call structure also persisted in the absence of noise. Two days after the noise was removed, experimental nestlings produced calls that were narrower in frequency range and less complex than control nestlings. We found no difference in growth between experimental and control nestlings.
Our results suggest that long-term noise exposure affects the structure of nestling begging calls. These effects persist in the absence of noise, suggesting that noise may affect how calls develop.

Vigilance benefits and competition costs in groups: do individual redshanks gain an overall foraging benefit?

Auteur(s): Sansom, A; Cresswell, W; Minderman, J; Lind, J
Bron: ANIMAL BEHAVIOUR, 75: 1869-1875, Part 6; JUN 2008
Abstract: Animals gain antipredation benefits from being in larger groups through increased probability of predator detection, dilution of individual risk of being attacked and confusion of predators during attack. A further benefit is that individuals in larger groups can decrease the amount of time they spend being vigilant, while maintaining a high probability of predator detection. They may then gain extra time to forage, so increasing overall intake rate.
Increasing group size, however, can also increase competition so that intake rates decrease.

We investigated whether there was a foraging benefit in redshanks, Tringa totanus, that show the group size decrease in individual vigilance. Intake rates did not change with group size, despite an increase in time spent foraging. Interference competition increased with group size because individuals travelled more to find prey. Redshanks used the extra time available to forage to maintain intake rates under increased competition.
Although the group size effect on vigilance did not accrue direct foraging benefits, larger groups formed, conferring other antipredation benefits. Intake rates were maintained because the interference competition was compensated by the benefits of reduced individual vigilance.
(c) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Who Dares Sings, And Who Sings Wins: Bold Birds Get The Girl

Humans often choose partners based on behavioural keys that are displayed during social interactions. The way we behave in different social contexts can reflect personality traits or temperament that may inspire long-term love. Behavioural norms that we perceive as sexually attractive are not culturally or evolutionarily arbitrary.

However, personality-mediated sexual selection is not just the privilege of mankind. In a new study László Garamszegiand colleagues at the University of Antwerp and at Eötvös University, Budapest used bird song as a model to investigate whether behavioural traits involved in sexual advertisement can serve as good indicators of personality in wild animals.

Lees meer: Science Daily

Full article: PLoS ONE

Superfast Muscles Power Songbird Singing

Some songbirds can contract their vocal muscles with the fastest muscle movements yet described — about 100 times faster than humans can blink an eye, according to new research.

The study found that two types of songbirds produce their tunes with superfast muscles, similar to those used by rattlesnakes, several fish and the ringdove (a type of pigeon).

Lees meer: Live Science

Birds Migrate Together At Night In Dispersed Flocks, New Study Indicates

A new analysis indicates that birds don’t fly alone when migrating at night. Some birds, at least, keep together on their migratory journeys, flying in tandem even when they are 200 meters or more apart.

The study, from researchers at the University of Illinois and the Illinois Natural History Survey, appears in Integrative and Comparative Biology in July. It is the first to confirm with statistical data what many ornithologists and observers had long suspected: Birds fly together in loose flocks during their nocturnal migration.

Lees meer: Science Daily

Migrating Songbirds Learn Survival Tips On The Fly

Migrating songbirds take their survival cues from local winged residents when flying through unfamiliar territory, a new Queen's University-led study shows.

It's a case of "When in Rome, do as the Romans do," says biologist Joseph Nocera, who conducted the research while working as an NSERC Postdoctoral Fellow at Queen's under the supervision of Biology professor Laurene Ratcliffe.

Avoiding predators can substantially increase a bird's chances of survival during migration, notes Dr. Nocera. But to do that, it first has to recognize who its predators are. "We believe some prey use social cues from other animals to gain information about potential predators," he says.

Lees meer:	Science Daily
	National Geographic News

Island Birds Can Adapt to Predators, Study Suggests

An island bird in New Zealand is able to change its nesting behavior to outwit predators—offering a ray of hope for island species worldwide facing threats from exotic invaders—researchers have discovered.

Melanie Massaro, a biologist at the University of Canterbury, and her co-authors found that New Zealand bellbird mothers spend longer periods of time on their nests when the risk of predation rises.

Lees meer: National Geographic News

Birds communicate reproductive success in song

Some migratory songbirds figure out the best place to live by eavesdropping on the singing of others that successfully have had baby birds – a communication and behavioral trait so strong that researchers playing recorded songs induced them to nest in places they otherwise would have avoided.

This suggests that songbirds have more complex communication abilities than had previously been understood, researchers say, and that these "social cues" can be as or more important than the physical environment of a site.

Lees meer: Biology News Net

SORA - Searchable Ornithological Research Archive

A full text searchable ornithological archive with following journals:

• Auk (1884-1999)
• Condor (1899-2000)
• Wader Studies Group Bulletin (1970-2004)
• Journal of Field Ornithology (1930-1999)
• Journal of Raptor Research (1967-2005)
• North American Bird Bander (1976-2000)
• Ornithological Monographs (1964-2005)
• Pacific Coast Avifauna (1900-1974)
• Studies in Avian Biology (1978-1999)
• Western Birds (1970-2004)
• Wilson Bulletin (1889-1999)

SORA

The watchman's song

Soldiers on sentry duty in hostile territory keep in regular radio contact with their colleagues to assure them that all is well and that they are safe to carry on their manoeuvres. New research by Dr Andy Radford of the School of Biological Sciences reveals that this is also a feature of the bird world.

Lees meer: Physorg.com

A flyway perspective on food resource abundance in a long-distance migrant, the Eurasian teal ( Anas crecca )

Auteur(s): Céline Arzel, Johan Elmberg, Matthieu Guillemain, Michel Lepley, Fabrice Bosca, Pierre Legagneux and Jean-Baptiste Nogues
Bron: JOURNAL OF ORNITHOLOGY Online First DOI 10.1007/s10336-008-0318-6
Abstract: Two frequent assumptions about the evolution of long-distance migration in birds are that they travel long distances annually to reach food-rich areas for breeding, and that they time their migratory journey to be at staging sites when the latter provide the best feeding conditions. These assumptions have rarely been properly tested, and there is no study in which a species’ major food types have been measured by standardized methods throughout a flyway and over a large part of the year.
We here present such data for Eurasian teal (Anas crecca), converted to a common energetic currency, and collected at wintering, spring staging and breeding sites. Teal did not time migration to maximize local food abundance; most birds left wintering and spring staging sites before a sharp increase in invertebrate food abundance occurred. On the other hand, hatching of ducklings coincided with a peak in invertebrate food abundance on boreal breeding lakes. Mean overall food abundance (invertebrates and seeds combined) did not differ between wintering sites in southern France and breeding sites in northern Sweden at the time of breeding.
Our results are inconsistent with the hypothesis that long-distance migration in dabbling ducks has evolved because adult birds gain an immediate pay-off in increased food abundance by flying north in spring. However, our data confirm a selective advantage for breeding at higher latitudes, because hatching of ducklings may coincide with a peak in invertebrate emergence and because longer days may increase the duration of efficient foraging.

Fuel stores, fuel accumulation, and the decision to depart from a migration stopover site

Auteur(s): Schaub, M; Jenni, L; Bairlein, F
Bron: BEHAVIORAL ECOLOGY, 19 (3): 657-666; MAY-JUN 2008
Abstract: Birds usually migrate by alternating flight bouts and stopovers for refueling. The decision when to leave a stopover place is of paramount importance for the success of migration. Despite its importance, little is known about which factors influence the departure decision. Using capture-recapture data of passerines from 3 stopover sites, we investigate by capture-recapture models whether this decision is dependent on actual fuel stores and fuel deposition rates. Individuals that accumulated fuel stores at medium rates departed later than individuals that either lost fuel stores during their stopover or able to increase their fuel stores quickly. This pattern was consistent among all sites. The departure decision was not dependent on actual fuel stores at 2 stopover sites. At the site facing an ecological barrier, emigration probability increased with increasing fuel stores, indicating that birds wait until they reach a threshold of fuel stores before departing.
There was a positive correlation between departure fuel load and fuel deposition rate at all sites, which is in accordance with the time-minimizing hypothesis.
These results suggest that the decision to depart from a stopover site is based on rather simple behavioral rules: birds that lose fuel stores or that increase fuel stores at a high rate would leave a site quickly, whereas birds increasing fuel stores at intermediate rates would stay for a longer time. The departure decision is shaped also by the position of the stopover site in relation to the next one and may be affected further by environmental factors.

Plasticity of moult and breeding schedules in migratory European Stonechats Saxicola rubicola

Auteur(s): HEINER FLINKS, BARBARA HELM, PETER ROTHERY
Bron: IBIS OnlineEarly Articles doi:10.1111/j.1474-919X.2008.00833.x
Abstract: Timing is crucial in seasonal environments. Passerine birds typically use a combination of physiological mechanisms and environmental cues to ensure that breeding, moult and migration occur without major temporal overlap and under the most favourable conditions. However, late in the breeding season some individuals initiate additional clutches , whereas others initiate moult. Such alternative strategies are thought to reflect trade-offs between reproductive benefits and timely investment in maintenance and survival. The degree of seasonal plasticity differs between species, depending on the mechanisms that govern their annual routine. Migrants are generally under pressure to complete breeding and moult before the autumn departure and often show little plasticity.
We studied seasonal plasticity of breeding and moult schedules in the European Stonechat Saxicola rubicola. This species, an obligate short-distance migrant in Central Europe, sometimes initiates late clutches after typically at least two earlier breeding attempts. Based on life-history theory and on observations in captivity, which revealed photoperiodic regulation of breeding and moult, we predicted relatively little seasonal plasticity in Stonechats. We further predicted that reproductive gains of late breeders should be offset by reduced survival. These predictions were tested on long-term field data, using Underhill–Zucchini models to estimate moult. Late breeding occurred in c. 40% of pairs and increased their reproductive success by a third.
Both sexes modified moult timing but in different ways. Late breeding females postponed moult approximately until chick independence without compensating for delay by faster moult. Males started moult on time and overlapped it with breeding, associated with markedly slowed plumage change. Sex differences in moult score increased with lay date, but due to their respective modifications, both sexes delayed moult completion. Nonetheless, we could not detect any evidence for survival costs of late breeding.
Breeding and moult of European Stonechats appear relatively flexible, despite migratory schedules and photoperiodic programs for seasonal timing. Individuals can modify seasonal behaviour in late summer, presumably depending on their condition, and may profit considerably from extended breeding.

Complete 'family tree' of all British birds gives clues about which species might be endangered next

A new complete evolutionary 'family tree' showing how all British bird species are related to each other may provide clues about which ones are at risk of population decline, according to new research published today (11 June) in Proceedings of the Royal Society B: Biological Sciences.

Comparing the new family tree with existing lists of endangered bird species, author Dr Gavin Thomas from the NERC Centre for Population Biology at Imperial College London found that British birds currently suffering population decline were clustered close together on the same branches of the family tree.

Lees meer: Biology News Net

New Zealand Bird Outwits Alien Predators

New research led by Dr Melanie Massaro and Dr Jim Briskie at the University of Canterbury, which found that the New Zealand bellbird is capable of changing its nesting behaviour to protect itself from predators, could be good news for island birds around the world at risk of extinction.

The introduction of predatory mammals such as rats, cats and stoats to oceanic islands has led to the extinction of many endemic island birds, and exotic predators continue to threaten the survival of 25 percent of all endangered bird species worldwide.

Lees meer: Science Daily

Loch Garten ospreys live

The osprey nest at the top of a tree at Loch Garten.

RSPB Abernethy Forest nature reserve

• The female osprey, 'EJ', arrived back at the nest on 26 March
• The first egg was laid on the morning of 18 April. The chicks hatched on 24 May, 26 May and 29 May. For the latest news, please read our blog
• Ospreys survive solely on fish
• Ospreys travel thousands of miles from African wintering grounds to breed here
• They are mainly found in Scotland, but also in the English Lake District, Rutland Water in the English Midlands and at Glaslyn in north Wales

RSPB Live Video

The Cormorant -- The 'Black Plague' Or An Example Of Successful Species Conservation?

Europe requires a common management strategy for cormorants in order to reconcile nature conservation and fishing interests. An effective regulation of cormorant populations can only work at the European level, researchers from the Helmholtz Centre for Environmental Research (UFZ) write in the scientific journal Environmental Conservation. Furthermore, they suggest a five-step action plan, which would start with a consensus on the real numbers of animals and end in an international management plan.

Currently a common solution is not materialising because of too many different interests from individual countries and a lack of coordination, according to UFZ researchers. In North America by comparison, a management plan for the Double-crested Cormorant has been in operation since 2003, although the problem there is just as complex as it is in Europe. The size of the cormorant population in Europe varies between half a million and one and a half million birds, depending on who provides the data. The researchers’ vision of a new action plan materialised from 22 interviews conducted with responsible persons from several EU countries at different management levels.

Lees meer: Science Daily

For barn swallows, feathers make the man

A new study led by the University of Colorado at Boulder has shown the testosterone of male North American barn swallows skyrocketed early in the breeding season when their breast colors were artificially enhanced by researchers, indicating the clothes -- or in this case, the feathers -- make the man.

The swallows, whose breast feathers were darkened to a deep red known to be most attractive to females, likely had more testosterone racing through their bodies because of amorous interactions with the opposite sex and more run-ins with jealous males, said CU-Boulder Assistant Professor Rebecca Safran, lead study author. The jump in testosterone was unexpected because it was observed at the time in the breeding cycle when levels of sex steroids like testosterone are typically declining, she said.

Lees meer: Biology News Net

Antarctic Melt Releasing DDT, Tainting Penguins

Poisonous chemicals that had been locked in ice for decades are now being released as climate change melts Antarctic glaciers, researchers report.

The chemicals, including the pesticide DDT, are seeping into the polar ecosystem and finding their way into wildlife populations.
Scientists made the discovery when studying the levels of pollutants in the fat and eggs of Adélie penguins.

Lees meer: National Geographic News

The eagles have landed - online!

A new webcam trained on a family of Spanish Imperial Eagles Aquila adalberti will aid the Alzando el vuelo (Taking off) conservation programme. The camera will raise the project's profile by affording web-surfers unique views of the mighty raptors.

The nest is located in the Cabañeros National Park (Spain), in the centre of the Iberian Peninsula, and is home to a pair of Spanish Imperial Eagles and their young chick. By entering the website people will be able to watch the birds 24 hours a day. Precautions were undertaken to ensure the pair were not disturbed during the cameras installation, and it is expected that the offspring will fledge around mid June.

Lees meer: BirdLife International

Visit the webcam

Un-paint it black: Avian prey as a component of the diet of nestling Hooded Crows Corvus cornix

Auteur(s): Zduniak, P; Kosicki, JZ; Goldyn, B
Bron: BELGIAN JOURNAL OF ZOOLOGY, 138 (1): 85-89; JAN 2008
Abstract: The Hooded Crow (Corvus cornix) is often considered the main nest predator of many bird species, especially waterbirds. Such relationship should be particularly clear during the breeding season in wetlands, when the need to supply their nestlings with the highest quality foods forces predators to intensify their hunting activities.
Hence, waterbirds should be their basic prey. We examined the composition of the diet of nestling Hooded Crows in the flooded river valley of the "Ujscie Warty" National Park in western Poland, which is a bird refuge of international importance and provides nesting habitat for numerous bird species.
Despite the richness of potential avian prey, the dominant components of Hooded Crow nestlings' diet were insects, fish and plants. Contrary to expectations, birds were only supplementary to the diet of nestlings, and thus, we suggest that crows are likely to have only a marginal influence on nest failures of potential avian prey species in regions similar to the studied area.

Human Vision Inadequate For Research On Bird Vision

The most attractive male birds attract more females and as a result are most successful in terms of reproduction. This is the starting point of many studies looking for factors that influence sexual selection in birds. However, is it reasonable to assume that birds see what we see? In a study published in the latest issue of American Naturalist, Uppsala researchers show that our human vision is not an adequate instrument.

"The results mean that many studies on sexual selection may need to be re-evaluated," says Anders Odeen, research assistant at the Department of Animal Ecology at Uppsala University, who carried out this study with his colleague Olle Håstad.

Lees meer: Science Daily

Shorebirds "Defy Gravity" to Eat

As Charles Darwin showed nearly 150 years ago, bird beaks are exquisitely adapted to the birds' feeding strategy. A team of MIT mathematicians and engineers has now explained exactly how some shorebirds use their long, thin beaks to defy gravity and transport food into their mouths.

The phalarope, commonly found in western North America, takes advantage of surface interactions between its beak and water droplets to propel bits of food from the tip of its long beak to its mouth, the research team reports in the May 16 issue of Science.

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TEDTalks : The amazing intelligence of crows - Joshua Klein (2008)

Hacker and writer Joshua Klein is fascinated by crows. (Notice the gleam of intelligence in their little black eyes?) After a long amateur study of corvid behavior, he's come up with an elegant machine that may form a new bond between animal and human.

Video: Ted Talks

Recipe For Energy Saving Unravelled In Migratory Birds

Pointed wings together with carrying less weight per wing area and avoidance of high winds and atmospheric turbulence save a bird loads of energy during migration. This has been shown for the first time in free-flying wild birds by researchers at Princeton University, the University of Montana, and the German Max Planck Institute for Ornithology. They state that climate change might have a critical impact on small migrants' energy budgets if it causes higher winds and atmospheric instability as predicted.

Lees meer: Science Daily

Seagulls: Are males the weaker sex?

Male seagulls may be more vulnerable to their environment during embryonic development than females, according to Maria Bogdanova and Ruedi Nager from the University of Glasgow in the UK. Until now, the sex differences in developmental rate and susceptibility to unfavorable conditions during the embryonic stage in birds have received little attention. The paper has just been published in Springer’s journal, Behavioral Ecology and Sociobiology.

In many birds, siblings hatch at different times, resulting in age hierarchies within broods, with younger chicks often suffering reduced competitive ability and poorer survival compared to older siblings. During the last phase of incubation, birds’ auditory system is developed and embryos communicate with each other by auditory stimuli. These vocalizations may act as a cue for later-developing embryos about forthcoming competition, and there is evidence that they can respond to these cues by accelerating their hatching time, to reduce their age disadvantage. However, it is unclear whether this flexibility in developmental rates is sex-specific.

Bogdanova and Nager experimentally manipulated the social environment of herring gull embryos and tested whether sibling contact during the embryonic stage affects the developmental rate of males and females differently, and whether this has consequences for their post-hatching performance. The last-laid eggs – female gulls commonly lay three eggs - were incubated either alone with no information about the presence of older siblings (experimental group), or in contact with other eggs which provided information about the presence of more advanced embryos (control group, replicating natural conditions). Post-hatching, the chicks were reared either with nest mates or alone.

The researchers found a sex-specific effect of social environment on hatching duration and fledging* condition. When incubated in isolation, males hatched faster than females but both sexes fledged in similar, relatively good, condition. In contrast, when incubated with normal between-embryo contact, males were unable to hatch as fast and fledged in significantly poorer condition than females, regardless of whether they were reared singly or in a brood.

The authors conclude that their findings confirm that there are differences in the way male and female herring gull chicks respond to the challenges of hatching at different times. It would appear that females have the upper hand.

Zie ook: Biology News

Great tits cope well with warming

At least one of Britain's birds appears to be coping well as climate change alters the availability of a key food.

Researchers found that great tits are laying eggs earlier in the spring than they used to, keeping step with the earlier emergence of caterpillars.

Writing in the journal Science, they point out that the same birds in the Netherlands have not managed to adjust.

Lees meer: BBC News

Marriage Crises In Blue Tits Are Probably Caused By Other Females

Divorce is widespread, not only in humans, but also in socially monogamous birds like the blue tit. Behavioural ecologists Mihai Valcu and Bart Kempenaers from the Max Planck Institute for Ornithology in Seewiesen found divorce rates of up to 50% in a long-term study of this species. But why do partners split up? To answer this question, it helps to know who suffers and who benefits from the separation.

Previous studies on small passerine birds, such as blue tits, have shown that females do better after divorce. This is because they had more offspring with a new partner. "These findings have led to the suggestion that the females should take the initiative to leave their partner", says Bart Kempenaers, Director of the Department Behavioural Ecology and Evolutionary Genetics at the Max Planck Institute for Ornithology in Seewiesen.

Lees meer: Science Daily

Many Asian Vultures Close to Extinction, Survey Finds

Several species of Asian vulture will be extinct within a decade, new research warns.
The carrion-eating birds have been on the decline due to exposure to a common livestock drug.

Now a survey of vultures in northern and central India has found the birds' populations have plunged to near-extinction levels—one species is down 99.9 percent since surveys began in the 1990s.

"These species are in trouble," said Todd Katzner, director of conservation and field research at the National Aviary in Pittsburgh, Pennsylvania. "Ten years? It may be sooner."

The study appeared this week in the Journal of the Bombay Natural History Society.

Lees meer: National Geographic News

Birds Can Tell If You Are Watching Them -- Because They Are Watching You

In humans, the eyes are said to be the 'window to the soul', conveying much about a person's emotions and intentions. New research demonstrates for the first time that birds also respond to a human's gaze.

Predators tend to look at their prey when they attack, so direct eye-gaze can predict imminent danger. Julia Carter, a PhD student at the University of Bristol, and her colleagues, set up experiments that showed starlings will keep away from their food dish if a human is looking at it. However, if the person is just as close, but their eyes are turned away, the birds resumed feeding earlier and consumed more food overall.

Carter said "This is a great example of how animals can pick up on very subtle signals and use them to their own advantage".


Lees meer: Science Daily

Birds Can Detect Predators Using Smell

Many animal species detect and avoid predators by smell, but this ability has largely been ignored in the study of birds, since it was traditionally thought that they did not make use of this sense. However, it has now been discovered that birds are not only capable of discerning their enemies through chemical signals, but that they also alter their behaviour depending on the perceived level of risk of predation.

The use of smell to detect chemical signals can be useful for birds in various situations, such as feeding and orientation. However, they can greatly increase their chances of survival if they can tell whether or not the smell they have detected is associated with a predator. Luisa Amo de Paz, the study’s lead author, explained that: “Birds can detect the presence of a predator” thanks to their sense of smell. Working as a biologist at the Spanish National Research Council’s (CSIC) Natural History Museum while the study was carried out, Ms. Amo de Paz is currently working for the Netherlands Institute of Ecology (NIOO-KNAW).

The research, published in the latest issue of Functional Ecology, provides the first ever evidence to show that birds are able to distinguish their predators using chemical signals. According to the researchers at the CSIC’s Natural History Museum, this study “opens up a new and promising area of research in understanding numerous aspects of bird behaviour, which have been ignored until now.”


Lees meer: Science Daily

Birds announce their sentry duty to help comrades get a good meal

Soldiers on sentry duty in hostile territory keep in regular radio contact with their colleagues to assure them that all is well and that they are safe to carry on their manoeuvres. New research funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and published in Current Biology today (17 April) reveals that this is also a feature of the bird world and is very likely to be a rare example of truly cooperative behaviour.

Researchers from the University of Bristol, led by BBSRC David Phillips Fellow Dr Andy Radford, have demonstrated that by giving the distinctive ‘watchman’s song’, individuals scanning for danger as sentinels ensure that their group-mates can focus on foraging, and so capture more food. Dr Radford said: “These exciting results point to a great example of true cooperation. The unselfish behaviour of the sentry is probably rewarded down the line by the improved survival of group mates, which leads to a larger group size. This increases the sentinel’s chances of survival when the group is under attack from predators or having to repel rivals from their territory. It’s a win-win scenario!”


Lees meer: Biology News

Migratory Birds Make Mistakes In Direction, But Not Distance

Migratory birds make mistakes in terms of direction, but not distance. These are the findings of a team of ornithologists and ecologists from the University of Marburg, the Ornithological Society in Bavaria and the Helmholtz Centre for Environmental Research (UFZ), writing in the Journal of Ornithology. The scientists assessed several thousand reports of Asian birds from the leaf-warbler and thrush families that had strayed to Europe. They discovered that the distance between the breeding grounds in northern Siberia and the wintering sites in southern Asia was often similar to the distance between the breeding grounds and Europe. The more similar the distances and the more numerous a particular species, the higher the probability of this species of bird straying to Europe.

Lees meer: Science Daily

Effect of nestbox type on occupancy and breeding biology of Tree Sparrows Passer montanus in central Spain

Auteur(s): Garcia-Navas, V; Arroyo, L; Sanz, JJ; et al.
Bron: IBIS 150 (2): 356-364 APR 2008
Abstract: Avian life-history studies are often conducted on populations nesting in nestboxes. However, the type of nestbox used is a potentially confounding variable, as each model shows specific characteristics.

In recent decades, a new commercial model of artificial nestbox made of woodcrete, a mixture of sawdust and additives, has become popular owing to its better protection against predators compared with the classic wooden design. We assess the effect of nestbox type on the breeding ecology of Tree Sparrows Passer montanus, focusing on their thermal properties, an influential factor in nestbox selection. Occupancy rates and reproductive parameters of Tree Sparrows were compared between birds breeding in woodcrete and wooden nestboxes over 5 years.

Woodcrete nestboxes had a higher occupancy rate and birds breeding in them had earlier clutches, a shorter incubation period and more reproductive attempts per season than birds nesting in wooden boxes. Clutch size and nestling condition did not differ between nestbox types, but reproductive success was higher in woodcrete nestboxes. The higher temperature in woodcrete nestboxes (1.5 degrees C higher on average) might explain these differences. Such differences may bias results obtained in comparative studies where more than one nestbox type is used.

Birdfeeders Can Both Help And Harm Bird Populations

Millions of people tend bird feeders in their backyards each year, often out of a desire to help the animals. But a new survey of research on the topic finds that feeding may not always bring a positive outcome for the birds.

In many cases, bird feeding was shown to have immediate positive outcomes. A number of studies indicated, for example, that chicks which were given supplemental food were far more likely to fledge than those that were not given extra food.

But feeding is a complex business and can lead birds to make poor decisions later in life. Attractive feeders can become ecological traps, encouraging birds to settle in an area that cannot support them once supplemental feeding has stopped. In those cases, feeders create a population level that cannot be sustained by natural levels of food.

Lees meer: Science Daily